Worm preventing HJT from running

Cant remember the name of the worm...if it is going to help I can do another online scan.

Anyway I wanted ya'll to check my computer so I downloaded HiJackThis and installed it, but nothing happens when I try opening/running it. I checked the FAQ's at Trend website, they suggested renaming it then run it. I have tried to rename it before installing, after installing, thru the properties menu, and still it won't do a thing. I also downloaded the exe, installer, and zip folder tried the above on all three formats.